I have a 10" 30 Herrett also. I make all my own brass from R-P brass. Size, trim, ream neck, fire form, then size to chamber. My most accurate load so far is with Nosler 125gr.BT over 23.0 grs. of H-4227 with Fed. 210 Primers & 2.320 OAL. I tried 3 different powders, H-4227 was the best. The 3 other bullets that shot good were ( Horn. 130 SSP, Speer 130 HP & Sierra 135 SSP ) they all hit in the same point of impact as the Noslers. Haven't tried any heavier bullets yet. Get an old copy of a T/C loading book, it has alot of info on the 30 Herrett. GOOD LUCK!!!